Apparatus and methods for radially expanding a tubular member

ABSTRACT

Radially expanding a tubular ( 12 ) such as a liner or casing, especially in a downward direction. The apparatus includes at least one driver device ( 20, 22 ) such as a piston that is typically fluid-actuated, and an expander device ( 14 ) is attached to the or each driver device ( 20, 22 ). Actuation of the or each driver device ( 20, 22 ) causes movement of the expander device ( 14 ) to expand the tubular ( 12 ). One or more anchoring devices ( 36, 40 ), which may be radially offset, are used to substantially prevent the tubular ( 12 ) from moving during expansion thereof.

[0001] The present invention relates to apparatus and methods that areparticularly, but not exclusively, suited for radially expandingtubulars in a borehole or wellbore. It will be noted that the term“borehole” will be used herein to refer also to a wellbore.

[0002] It is known to use an expander device to expand at least aportion of a tubular member, such as a liner, casing or the like, toincrease the inner and outer diameters of the member. Use of the term“tubular member” herein will be understood as being a reference to anyof these and other variants that are capable of being radially expandedby the application of a radial expansion force, typically applied by theexpander device, such as an expansion cone.

[0003] The expander device is typically pulled or pushed through thetubular member to impart a radial expansion force thereto in order toincrease the inner and outer diameters of the member. Conventionalexpansion processes are generally referred to as “bottom-up” in that theprocess begins at a lower end of the tubular member and the cone ispushed or pulled upwards through the member to radially expand it. Theterms “upper” and “lower” shall be used herein to refer to theorientation of a tubular member in a conventional borehole, the termsbeing construed accordingly where the borehole is deviated or a lateralborehole for example. “Lower” generally refers to the end of the memberthat is nearest the formation or pay zone.

[0004] The conventional bottom-up method has a number of disadvantages,and particularly there are problems if the expander device becomes stuckwithin the tubular member during the expansion process. The device canbecome stuck for a number of different reasons, for example due torestrictions or protrusions in the path of the device.

[0005] In addition to this, there are also problems with expandingtubular members that comprise one or more portions of member that areprovided with perforations or slots (“perforated”), and one or moreportions that are not provided with perforations or slots(“non-perforated”), because the force required to expand a perforatedportion is substantially less than that required to expand anon-perforated portion. Thus, it is difficult to expand combinations ofperforated and non-perforated tubular members using the same expanderdevice and method.

[0006] Some methods of radial expansion use hydraulic force to propelthe cone, where a fluid is pumped into the tubular member down through aconduit such as drill pipe to an area below the cone. The fluid pressurethen acts on a lower surface of the cone to provide a propulsionmechanism. It will be appreciated that a portion of the liner to beexpanded defines a pressure chamber that facilitates a build up ofpressure below the cone to force it upwards and thus the motive power isapplied not only to the cone, but also to the tubular member that is tobe expanded. It is often the case that the tubular members are typicallycoupled together using screw threads and the pressure in the chamber cancause the threads between the portions of tubular members to fail.Additionally, the build up of pressure in the pressure chamber can causestructural failure of the member due to the pressure within it if thepressure exceeds the maximum pressure that the material of the membercan withstand. If the material of the tubular bursts, or the threadfails, the pressure within the pressure chamber is lost, and it is nolonger possible to force the cone through the member using fluidpressure.

[0007] Also, in the case where the cone is propelled through the linerusing fluid pressure, where the outer diameter of the tubular memberdecreases, the surface area of the cone on which the fluid pressure canact is reduced accordingly because the size of the expander device mustbe in proportion to the size of the tubular member to be expanded.

[0008] According to a first aspect of the present invention, there isprovided apparatus for radially expanding a tubular, the apparatuscomprising one or more driver devices coupled to an expander device, andone or more anchoring devices engageable with the tubular, wherein thedriver device causes movement of the expander device through the tubularto radially expand it whilst the anchoring device prevents movement ofthe tubular during expansion.

[0009] In this embodiment, the or each anchoring device optionallyprovides a reaction force to the expansion force generated by the oreach driver.

[0010] According to a second aspect of the present invention, there isprovided apparatus for radially expanding a tubular, the apparatuscomprising one or more driver devices coupled to an expander device, andone or more anchoring devices engageable with the tubular, wherein theor each driver device causes movement of the expander device through thetubular to radially expand it whilst the anchoring device provides areaction force to the expansion force generated by the or each driverdevice.

[0011] In this embodiment, at least one anchoring device optionallyprevents movement of the tubular during expansion.

[0012] According to a third aspect of the present invention, there isprovided a method of expanding a tubular, the method comprising the stepof actuating one or more driver devices to move an expander devicewithin the tubular to radially expand the member.

[0013] The invention also provides apparatus for radially expanding atubular, the apparatus comprising one ore more driver devices that arecoupled to an expander device, where fluid collects in a fluid chamberand acts on the or each driver device to move the expander device.

[0014] The invention further provides a method of radially expanding atubular, the method comprising the steps of applying pressurised fluidto one ore more driver devices that are coupled to an expander device,where fluid collects in a fluid chamber and acts on the or each driverdevice to move the expander device.

[0015] This particular embodiment has advantages in that the pressurisedfluid acts directly on the or each driver device and not on the tubularitself.

[0016] The or each driver device is typically a fluid-actuated devicesuch as a piston. The piston(s) can be coupled to the expander device byany conventional means. Two or more pistons are typically provided, thepistons typically being coupled in series. Thus, additional expansionforce can be provided by including additional pistons. The or eachpiston is typically formed by providing an annular shoulder on a sleeve.The expander device is typically coupled to the sleeve.

[0017] Optionally, one or more expander devices may be provided. Thus,the tubular can be radially expanded in a step-wise manner. That is, afirst expander device radially expands the inner and outer diameters ofthe member by a certain percentage, a second expander device expands bya further percentage and so on.

[0018] The sleeve is typically provided with ports that allow fluid froma bore of the sleeve to pass into a fluid chamber or piston area on oneside of the or each piston. Thus, pressurised fluid can be delivered tothe fluid chamber or piston area to move the or each piston.

[0019] The sleeve is typically provided with a ball seat. The ball seatallows the bore of the sleeve to be blocked so that fluid pressure canbe applied to the pistons via the ports in the sleeve.

[0020] The fluid chamber or piston area is typically defined between thesleeve and an end member. Thus, pressurised fluid does not act directlyon the tubular. This is advantageous as the fluid pressure required forexpansion may cause the material of the tubular to stretch or burst.Additionally, the tubular may be a string of tubular members that arethreadedly coupled together, and the fluid pressure may be detrimentalto the threaded connections.

[0021] The or each anchoring device is typically a one-way anchoringdevice. The anchoring device(s) can be, for example, a BALLGRA™manufactured by BSW Limited. The or each anchoring device is typicallyactuated by moving at least a portion of it in a first direction. Theanchoring device is typically de-actuated by moving said portion in asecond direction, typically opposite to the first direction.

[0022] The or each anchoring device typically comprises a plurality ofball bearings that engage in a taper. Movement of the taper in the firstdirection typically causes the balls to move radially outward to engagethe tubular. Movement of the taper in the second direction typicallyallows the balls to move radially inward and thus disengage the tubular.

[0023] Two anchoring devices are typically provided. One of theanchoring devices is typically laterally offset with respect to theother anchoring device. A first anchoring device typically engagesportions of the tubular that are unexpanded, and a second anchoringdevice typically engages portions of the tubular that have been radiallyexpanded. Thus, at least one anchoring device can be used to grip thetubular and retain it on the apparatus as it is being run into theborehole, and also during expansion of the member.

[0024] The apparatus is typically provided with a fluid path that allowstrapped fluid to bypass the apparatus. Thus, fluids trapped at one endof the apparatus can bypass it to the other end of the apparatus.

[0025] The expander device typically comprises an expansion cone. Theexpansion cone can be of any conventional type and can be made of anyconventional material (e.g. steel, steel alloy, tungsten carbide etc).The expander device is typically of a material that is harder than thetubular that it has to expand. It will be appreciated that only theportion(s) of the expander device that contact the tubular need be ofthe harder material.

[0026] The apparatus typically includes a connector for coupling theapparatus to a string. The connector typically comprises a boxconnection, but any conventional connector may be used. The stringtypically comprises a drill string, coiled tubing string, productionstring, wireline or the like.

[0027] The tubular typically comprises liner, casing, drill pipe etc,but may be any downhole tubular that is of a ductile material and/or iscapable of sustaining plastic and/or elastic deformation. The tubularmay be a string of tubulars (e.g. a string of individual lengths ofliner that have been coupled together).

[0028] The step of moving the piston(s) typically comprises applyingfluid pressure thereto.

[0029] The method typically includes the additional step of gripping thetubular during expansion. The step of gripping the tubular typicallycomprises actuating one or more anchoring devices to grip the tubular.

[0030] The method optionally includes one, some or all of the additionalsteps of a) reducing the fluid pressure applied to the pistons; b)releasing the or each anchoring device; c) moving the expander device toan unexpanded portion of the tubular; d) actuating the or each anchoringdevice to grip the tubular; and e) increasing the fluid pressure appliedto the pistons to move the expander device to expand the tubular.

[0031] The method optionally includes repeating steps a) to e) aboveuntil the entire length of the tubular is expanded.

[0032] Embodiments of the present invention shall now be described, byway of example only, with reference to the accompanying drawings, inwhich:

[0033]FIG. 1 is a longitudinal part cross-sectional view of an exemplaryembodiment of apparatus for expanding a tubular member;

[0034]FIG. 2 is a cross-sectional view through the apparatus of FIG. 1along line A-A in FIG. 1;

[0035]FIG. 3 is a cross-sectional view through the apparatus of FIG. 1along line B-B in FIG. 1; and

[0036] FIGS. 4 to 7 show a similar view of the apparatus of FIG. 1 invarious stages of operation thereof.

[0037] Referring to the drawings, there is shown an exemplary embodimentof apparatus 10 that is particularly suited for radially expanding atubular member 12 within a borehole (not shown). FIG. 1 shows theapparatus 10 in part cross-section and it will be appreciated that theapparatus 10 is symmetrical about the centre line C.

[0038] The tubular member 12 that is to be expanded can be of anyconventional type, but it is typically of a ductile material so that itis capable of being plastically and/or elastically expanded by theapplication of a radial expansion force. Tubular member 12 may compriseany downhole tubular such as drill pipe, liner, casing or the like, andis typically of steel, although other ductile materials may also beused.

[0039] The apparatus 10 includes an expansion cone 14 that may be of anyconventional design or type. For example, the cone 14 can be of steel oran alloy of steel, tungsten carbide, ceramic or a combination of thesematerials. The expansion cone 14 is typically of a material that isharder than the material of the tubular member 12 that it has to expand.However, this is not essential as the cone 14 may be coated or otherwiseprovided with a harder material at the portions that contact the tubular12 during expansion.

[0040] The expansion cone 14 is provided with an inclined face 14 i thatis typically annular and is inclined at an angle of around 20° withrespect to the centre line C of the apparatus 10. The inclination of theinclined face 14 i can vary from around 5° to 45° but it is found thatan angle of around 15° to 25° gives the best performance. This angleprovides sufficient expansion without causing the material to ruptureand without providing high frictional forces.

[0041] The expansion cone 14 is attached to a first tubular member 16which in this particular embodiment comprises a portion of coil tubing,although drill pipe etc may be used. A first end 16 a of the coil tubingis provided with a ball catcher in the form of a ball seat 18, thepurpose of which is to block a bore 16 b in the coil tubing 16 throughwhich fluid may pass.

[0042] The coiled tubing 16 is attached to a second tubular member inthe form of a sleeve 17 using a number of annular spacers 19 a, 19 b, 19c. The spacers 19 b and 19 c create a first conduit 52 therebetween, andthe spacers 19 a, 19 b create a second conduit 56 therebetween. Thespacer 19 c is provided with a port 50 and spacer 19 b is provided witha port 54, both ports 50, 54 allowing fluid to pass therethrough. Thefunction of the ports 50, 54 and the conduits 52, 56 shall be describedbelow.

[0043] Two laterally-extending annular shoulders are attached to thesleeve 17 and sealingly engage a cylindrical end member 24, the annularshoulders forming first and second pistons 20, 22, respectively. Thecylindrical end member 24 includes a closed end portion 26 at a firstend thereof. The engagement of the first and second pistons 20, 22 withthe cylindrical end member 24 provides two piston areas 28, 30 in whichfluid (e.g. water, brine, drill mud etc) can be pumped into via vents32, 34 from the bore 16 b. The annular shoulders forming the first andsecond pistons 20, 22 can be sealed to the cylindrical end member 24using any conventional type of seal (e.g. O-rings, lip-type seals or thelike).

[0044] The two piston areas 28, 30 typically have an area of around 15square inches, although this is generally dependent upon the dimensionsof the apparatus 10 and the tubular member 12, and also the expansionforce that is required.

[0045] A second end of the cylindrical end member 24 is attached to afirst anchoring device 36. The first anchoring device 36 is typically aBALLGRA™ that is preferably a one-way anchoring device and is suppliedby BSW Limited. The BALLGRA™ works on the principle of a plurality ofballs that engage in a taper. Applying a load to the taper in a firstdirection acts to push the balls radially outwardly and thus they engagean inner surface 12 i of the tubular 12 to retain it in position. Thegripping motion of the BALLGRAB™ can be released by moving the taper ina second direction, typically opposite to the first direction, so thatthe balls disengage the inner surface 12 i.

[0046] The weight of the tubular member 12 can be carried by the firstanchoring device 36 as the apparatus 10 is being run into the borehole,but this is not the only function that it performs, as will bedescribed. The first anchoring device 36 is typically a 7 inch(approximately 178 mm), 29 pounds per foot type, but the particular sizeand rating of the device 36 that is used generally depends upon thesize, weight and like characteristics of the tubular member 12.

[0047] The first anchoring device 36 is coupled via a plurality ofcircumferentially spaced-apart rods 38 (see FIG. 2 in particular) to asecond anchoring device 40 that in turn is coupled to a portion ofconveying pipe 42. The second anchoring device 40 is typically of thesame type as the first anchoring device 36, but could be different as itis not generally required to carry the weight of the member 12 as theapparatus 10 is run into the borehole.

[0048] The conveying pipe 42 can be of any conventional type, such asdrill pipe, coil tubing or the like. The conveying pipe 42 is providedwith a connection 44 (e.g. a conventional box connection) so that it canbe coupled into a string of, for example drill pipe, coiled tubing etc(not shown). The string is used to convey the apparatus 10 and thetubular member 12.

[0049] The second anchoring device 40 is used to grip the tubular member12 after it has been radially expanded and is typically located on alongitudinal axis that is laterally spaced-apart from the axis of thefirst anchoring device 36. This allows the second anchoring device 40 toengage the increased diameter of the member 12 once it has been radiallyexpanded.

[0050] Referring now to FIGS. 4 to 7, the operation of apparatus 10shall now be described.

[0051] A ball 46 (typically a ¾ inch, approximately 19 mm ball) isdropped or pumped down the bore of the string to which the conveyingpipe 42 is attached, and thereafter down through the bore 16 b of thecoil tubing 16 to engage the ball seat 18. The ball 46 therefore blocksthe bore 16 b in the conventional manner. Thereafter, the bore 16 b ispressured-up by pumping fluid down through the bore 16 b, typically to apressure of around 5000 psi. The ball seat 18 can be provided with asafety-release mechanism (e.g. one or more shear pins) that will allowthe pressure within bore 16 b to be reduced in the event that theapparatus 10 fails. Any conventional safety-release mechanism can beused.

[0052] The pressurised fluid enters the piston areas 28, 30 through thevents 32, 34 respectively and acts on the pistons 20, 22. The fluidpressure at the piston areas 28, 30 causes the coil tubing 16, sleeve 17and thus the expansion cone 14 to move to the right in FIG. 4 (e.g.downwards when the apparatus 10 is orientated in a conventionalborehole) through the tubular member 12 to radially expand the inner andouter diameters thereof, as illustrated in FIG. 4.

[0053] During movement of the pistons 20, 22, slight tension is appliedto the conveying pipe 42 via the drill pipe or the like to which theapparatus 10 is attached so that the first anchoring device 36 grips thetubular member 12 to retain it in position during the expansion process.Thus, the first anchoring device 36 can be used to grip the tubularmember 12 as the apparatus 10 is run into the borehole, and can alsoused to grip and retain the tubular member 12 in place during at least apart of the expansion process.

[0054] Continued application of fluid pressure through the vents 32, 34into the piston areas 28, 30 causes the pistons 20, 22 to move to theposition shown in FIG. 5, where an annular shoulder 48 that extends fromthe cylindrical end member 24 defines a stop member for movement of thepiston 20 (and thus piston 22). Thus, the pistons 20, 22 have extendedto their first stroke, as defined by the stop member 48. The length ofstroke of the pistons 20, 22 can be anything from around 5 ft(approximately 1 and a half metres) to around 30 ft (around 6 metres),but this is generally dependant upon the rig handling capability and thelength of member 12. The length of the stroke of the pistons 20, 22 canbe chosen to suit the particular application and may extend outwith therange quoted.

[0055] Once the pistons 20, 22 have reached their first stroke, theslight upward force applied to the conveying pipe 42 is released so thatthe first anchoring device 36 disengages the inner surface 12 i of thetubular member 12. Thereafter, the conveying pipe 42 and the anchoringdevice 36, 40 and end member 24 are moved to the right as shown in FIG.6 (e.g. downwards). This can be achieved by lowering the string to whichthe conveying pipe 42 is attached.

[0056] The second anchoring device 40 is positioned laterally outwardlyof the first anchoring device 36 so that it can engage the expandedportion 12 e of the tubular member 12. Thus, the tubular member 12 canbe gripped by both the first and second anchoring devices 36, 40, asshown in FIG. 6.

[0057] With the apparatus 10 in the position shown in FIG. 6, tension isthen applied to the conveying pipe 42 so that the first and secondanchoring devices 36, 40, are actuated to grip the inner surface 12 i ofthe member 12, and fluid pressure (at around 5000 psi) is then appliedto the bore 16 b to extend the pistons 20, 22. Fluid pressure iscontinually applied to the pistons 20, 22 via vents 32, 34 to extendthem through their next stroke to expand a further portion of thetubular member 12, as shown in FIG. 7.

[0058] This process is then repeated by releasing the tension on theconveying pipe 42 to release the first and second anchoring devices 36,40, moving them downwards and then placing the conveying pipe 42 undertension again to engage the anchoring devices 36, 40 with the member 12.The pressure in the bore 16 b is then increased to around 5000 psi toextend the pistons 20, 22 over their next stroke to expand a furtherportion of the tubular member 12.

[0059] The process described above with reference to FIGS. 5 to 7 iscontinued until the entire length of the member 12 has been radiallyexpanded. The second anchoring device 40 ensures that the entire lengthof the member 12 can be expanded by providing a means to grip the member12. The second anchoring device 40 is typically required as the firstanchoring device 36 will eventually pass out of the end of the member 12and cannot thereafter grip it. However, expansion of the member 12 intocontact with the borehole wall (where appropriate) may be sufficient toprevent or restrict movement of the member 12. A friction and/or sealingmaterial (e.g. a rubber) can be applied at axially spaced-apartlocations on the outer surface of the member 12 to increase the frictionbetween the member 12 and the wall of the borehole. Further, cement canbe circulated through the apparatus 10 prior to the expansion of member12 (as described below) so that the cement can act as a partial anchorfor the member 12 during and/or after expansion.

[0060] Apparatus 10 can be easily pulled out of the borehole once themember 12 has been radially expanded.

[0061] Embodiments of the present invention provide significantadvantages over conventional methods of radially expanding a tubularmember. In particular, certain embodiments provide a top-down expansionprocess where the expansion begins at an upper end of the member 12 andcontinues down through the member. Thus, if the apparatus 10 becomesstuck, it can be easily pulled out of the borehole without having toperform a fishing operation. The unexpanded portions of the tubular 12are typically below the apparatus 10 and do not prevent retraction ofthe apparatus 10 from the borehole, unlike conventional bottom-upmethods. This is particularly advantageous as the recovery of the stuckapparatus 10 is much simpler and quicker. Furthermore, it is less likelythat the apparatus 10 cannot be retrieved from the borehole, and thus itis less likely that the borehole will be lost due to a stuck fish. Theunexpanded portion can be milled away (e.g. using an over-mill) so thatit does not adversely affect the recovery of hydrocarbons, or a new orrepaired apparatus can be used to expand the unexpanded portion ifappropriate.

[0062] Also, conventional bottom-up methods of radial expansiongenerally require a pre-expanded portion in the tubular member 12 inwhich the expander device is located before the expansion processbegins. It is not generally possible to fully expand the pre-expandedportion, and in some instances, the pre-expanded portion can restrictthe recovery of hydrocarbons as it produces a restriction (i.e. aportion of reduced diameter) in the borehole. However, the entire lengthof the member 12 can be fully expanded with apparatus 10.

[0063] The purpose of the pre-expanded portion on conventional methodsis typically to house the expansion cone as the apparatus is being runinto the borehole. In certain embodiments of the invention, an end ofthe tubular member 12 rests against the expansion cone 14 as it is beingrun into the borehole, but this is not essential as the first anchoringdevice 36 can be used to grip the member 12 as apparatus 10 is run in.Thus, a pre-expanded portion is not required.

[0064] The apparatus 10 is a mechanical system that is drivenhydraulically, but the material of the tubular member 12 that has to beexpanded is not subjected to the expansion pressures during conventionalhydraulic expansion, as no fluid acts directly on the tubular member 12itself, but only on the pistons 20, 22 and the cylindrical end member24. Thus, the expansion force required to expand the tubular member 12is effectively de-coupled from the force that operates the apparatus 10.

[0065] Also in conventional systems, the movement of the expansion cone12 is coupled to the drill pipe or the like, in that the drill pipe orthe like is typically used to push or pull the expansion cone throughthe member that is to be expanded. However, with the apparatus 10, themovement of the expansion cone 12 is substantially de-coupled frommovement of the drill pipe, at least during movement of the cone 14during expansion. This is because the movement of the pistons 20, 22 byhydraulic pressure causes movement of the expansion cone 14; movement ofthe drill pipe or the like to which the conveying pipe 42 is coupled hasno effect on the expansion process, other than to move certain portionsof the apparatus 10 within the borehole.

[0066] If higher expansion forces are required, then additional pistonscan be added to provide additional force to move the expansion cone 14and thus provide additional expansion forces. The additional pistons canbe added in series to provide additional expansion force. Thus, there isno restriction on the amount of expansion force that can be applied asfurther pistons can be added; the only restriction would be the overalllength of the apparatus 10. This is particularly useful where the liner,casing and cladding are made of chrome as this generally requires higherexpansion forces. Also, the connectors between successive portions ofliner and casing etc that are of chrome are critical, and as thismaterial is typically very hard, it requires higher expansion forces.

[0067] The apparatus 10 can be used to expand small sizes of tubularmember 12 (API grades) up to fairly large diameter members, and can alsobe used with lightweight pipe with a relatively small wall thickness (ofless that 5 mm) and on tubulars having a relatively large wallthicknesses.

[0068] Furthermore, the hydraulic fluid that is used to move the pistons20, 22 can be recycled and is thus not lost into the formation.Conventional expansion methods using hydraulic or other motive powerscan cause problems with “squeeze” where fluids in the borehole that areused to propel the expander device, force fluids in the borehole belowthe device back into the formation, which can cause damage to theformation and prevent it from producing hydrocarbons.

[0069] However, the hydraulic fluid that is used to drive the pistons20, 22 is retained within the apparatus 10 by the hall 46, and thus willnot adversely effect the formation or pay zone.

[0070] In addition to this, apparatus 10 is provided with a path throughwhich fluid that may be trapped below the apparatus 10 (that is fluidthat is to the right of the apparatus 10 in FIG. 1) can flow through theapparatus 10 to the annulus above it (to the left in FIG. 1).

[0071] Referring to FIGS. 1 and 3 in particular, this is achieved byproviding one or more circumferentially spaced apart ports 50 that allowfluid to travel through the spacer 19 c and into the annular conduit 52,through the ports 54 in the spacer 19 b into the second conduit 56, andthen out into the annulus through a vent 58. Thus, fluid from below theapparatus 10 can be vented to above the apparatus 10, thereby reducingthe possibility of damage to the formation or pay zone, and alsosubstantially preventing the movement of the apparatus 10 from beingarrested due to trapped fluids.

[0072] Additionally, the apparatus 10 can be used to circulate fluidsbefore the ball 46 is dropped into the ball seat 18, and thus cement orother fluids can be circulated before the tubular member 12 is expanded.This is particularly advantageous as cement could be circulated into theannulus between the member 12 and the liner or open borehole that themember 12 is to engage, to secure the member 12 in place.

[0073] It will also be appreciated that a number of expansion cones 14can be provided in series so that there is a step-wise expansion of themember 12. This is particularly useful where the member 12 is to beexpanded to a significant extent, and the force required to expand it tothis extent is significant and cannot be produced by a single expansioncone. Although the required force may be achieved by providingadditional pistons (e.g. three or more), there may be a restriction inthe overall length of the apparatus 10 that precludes this.

[0074] The apparatus 10 can be used to expand portions of tubular thatare perforated and portions that are non-perforated. This is because thepressure applied to the pistons 20, 22 can be increased or decreased toprovide for a higher or lower expansion force. Thus, apparatus 10 can beused to expand sand screens and strings of tubulars that includeperforated and non-perforated portions.

[0075] Embodiments of the present invention provide advantages overconventional methods and apparatus in that the apparatus can be usedwith small sizes of tubulars. The force required to expand smalltubulars can be high, and this high force cannot always be provided byconventional methods because the size of the tubular reduces the amountof force that can be applied, particularly where the cone is being movedby hydraulic pressure. However, embodiments of the present invention canovercome this because the expansion force can be increased by providingadditional pistons.

[0076] Modifications and improvements may be made to the foregoingwithout departing from the scope of the present invention. For example,it will be appreciated that the term “borehole” can refer to any holethat is drilled to facilitate the recovery of hydrocarbons, water or thelike.

1. Apparatus for radially expanding a tubular comprising one or moredriver devices (20, 22) coupled to an expander device (14), and one ormore anchoring devices (36, 40) engageable with the tubular (12),wherein the driver device (20, 22) causes movement of the expanderdevice (14) through the tubular (12) to radially expand it whilst theanchoring device (36, 40) prevents movement of the tubular (12) duringexpansion.
 2. Apparatus according to claim 1, wherein the or eachanchoring device (36, 40) provides a reaction force to the expansionforce generated by the or each driver device (20, 22).
 3. Apparatusaccording to either preceding claim, wherein the or each driver device(20, 22) is a fluid-actuated device.
 4. Apparatus according to anypreceding claim, wherein the or each driver device comprises a piston(20, 22).
 5. Apparatus according to claim 4, wherein two or more pistons(20, 22) are provided, the pistons (20, 22) being coupled in series. 6.Apparatus according to claim 4 or claim 5, wherein the or each piston(20, 22) is formed by providing an annular shoulder on a sleeve (16,17).
 7. Apparatus according to claim 6, wherein the expander device (14)is coupled to the sleeve (16, 17).
 8. Apparatus according to claim 6 orclaim 7, wherein the sleeve (16, 17) is provided with ports (32, 34)that allow fluid from a bore (16 b) of the sleeve (16, 17) to pass intoa fluid chamber (28, 30) or piston area (28, 30) on one side of the oreach piston (20, 22).
 9. Apparatus according to claim 8, wherein thesleeve (16, 17) is provided with a ball seat (18).
 10. Apparatusaccording to claim 8 or claim 9, wherein the fluid chamber (28, 30) orpiston area (28, 30) is defined between the sleeve (16, 17) and an endmember (24, 26).
 11. Apparatus according to any preceding claim, whereintwo or more expander devices (14) are provided.
 12. Apparatus accordingto any preceding claim, wherein the or each anchoring device (36, 40) isa one-way anchoring device.
 13. Apparatus according to any precedingclaim, wherein the or each anchoring device (36, 40) is actuated bymoving at least a portion of it in a first direction.
 14. Apparatusaccording to claim 13, wherein the or each anchoring device (36, 40) isde-actuated by moving said portion in a second direction.
 15. Apparatusaccording to any preceding claim, wherein a first anchoring device (36)is laterally offset with respect to a second anchoring device (40). 16.Apparatus for radially expanding a tubular comprising one or more driverdevices (20, 22) coupled to an expander device (14), and one or moreanchoring devices (36, 40) engageable with the tubular (12), wherein theor each driver device (20, 22) causes movement of the expander device(14) through the tubular (12) to radially expand it whilst the anchoringdevice (36, 40) provides a reaction force to the expansion forcegenerated by the or each driver device (20, 22).
 17. Apparatus accordingto claim 16, wherein at least one anchoring device (36, 40) preventsmovement of the tubular (12) during expansion.
 18. Apparatus accordingto claim 16 or claim 17, wherein the or each driver device (20, 22) is afluid-actuated device.
 19. Apparatus according to any one of claims 16to 18, wherein the or each driver device comprises a piston (20, 22).20. Apparatus according to claim 19, wherein two or more pistons (20,22) are provided, the pistons (20, 22) being coupled in series. 21.Apparatus according to claim 19 or claim 20, wherein the or each piston(20, 22) is formed by providing an annular shoulder on a sleeve (16,17).
 22. Apparatus according to claim 21, wherein the expander device(14) is coupled to the sleeve (16, 17).
 23. Apparatus according to claim21 or claim 22, wherein the sleeve (16, 17) is provided with ports (32,34) that allow fluid from a bore (16 b) of the sleeve (16, 17) to passinto a fluid chamber (28, 30) or piston area (28, 30) on one side of theor each piston (20, 22).
 24. Apparatus according to claim 23, whereinthe sleeve (16, 17) is provided with a ball seat (18).
 25. Apparatusaccording to claim 23 or claim 24, wherein the fluid chamber (28, 30) orpiston area (28, 30) is defined between the sleeve (16, 17) and an endmember (24, 26).
 26. Apparatus according to any one of claims 16 to 25,wherein two or more expander devices (14) are provided.
 27. Apparatusaccording to any one of claims 16 to 26, wherein the or each anchoringdevice (36, 40) is a one-way anchoring device.
 28. Apparatus accordingto any one of claims 16 to 27, wherein the or each anchoring device (36,40) is actuated by moving at least a portion of it in a first direction.29. Apparatus according to claim 28, wherein the or each anchoringdevice (36, 40) is de-actuated by moving said portion in a seconddirection.
 30. Apparatus according to any one of claims 16 to 29,wherein a first anchoring device (36) is laterally offset with respectto a second anchoring device (40).
 31. Apparatus for radially expandinga tubular comprising one or more driver devices (20, 22) that arecoupled to an expander device (14), where fluid collects in a fluidchamber (28, 30) and acts on the or each driver device (20, 22) to movethe expander device (14).
 32. Apparatus according to claim 31, whereinthe or each driver device comprises a piston (20, 22).
 33. Apparatusaccording to 32, wherein two or more pistons (20, 22) are provided, thepistons (20, 22) being coupled in series.
 34. Apparatus according toclaim 32 or claim 33, wherein the or each piston (20, 22) is formed byproviding an annular shoulder on a sleeve (16, 17).
 35. Apparatusaccording to claim 34, wherein the expander device (14) is coupled tothe sleeve (16, 17).
 36. Apparatus according to claim 34 or claim 35,wherein the or each fluid chamber (28, 30) is formed on one side of theor each piston (20, 22) between the sleeve (16, 17) and an end member(24, 26).
 37. Apparatus according to claim 36, wherein the sleeve (16,17) is provided with ports (32, 34) that allow fluid from a bore (16 b)of the sleeve (16, 17) to pass into the or each fluid chamber (28, 30).38. Apparatus according to claim 37, wherein the sleeve (16, 17) isprovided with a ball seat (18).
 39. Apparatus according to any one ofclaims 31 to 38, wherein two or more expander devices (14) are provided.40. Apparatus according to any one of claims 31 to 39, wherein theapparatus includes one or more anchoring devices (36, 40) that canengage the tubular (12) to prevent movement of the tubular (12) duringexpansion.
 41. Apparatus according to claim 40, wherein the or eachanchoring device (36, 40) is actuated by moving at least a portion of itin a first direction.
 42. Apparatus according to claim 41, wherein theor each anchoring device (36, 40) is de-actuated by moving said portionin a second direction.
 43. Apparatus according to any one of claims 40to 42, wherein a first anchoring device (36) is laterally offset withrespect to a second anchoring device (40).
 44. A method of expanding atubular, the method comprising the step of actuating one or more driverdevices (20, 22) to move an expander device (14) within the tubular (12)to radially expand the tubular (12).
 45. A method according to claim 44,wherein the step of actuating the or each driver device (20, 22)comprises applying fluid pressure thereto.
 46. A method according toclaim 44 or claim 45, wherein the method includes the additional step ofgripping the tubular (12) during expansion.
 47. A method according toclaim 46, wherein the step of gripping the tubular (12) comprisesactuating one or more anchoring devices (36, 40) to grip the tubular(12).
 48. A method according to claim 47, the method including one, someor all of the additional steps of a) reducing the fluid pressure appliedto the or each driver device (20, 22); b) releasing the or eachanchoring device (36, 40); c) moving the expander device (14) to anunexpanded portion of the tubular (12); d) actuating the or eachanchoring device (36, 40) to grip the tubular (12); and e) increasingthe fluid pressure applied to the or each driver device (20, 22) to movethe expander device (14) to expand the tubular (12).
 49. A methodaccording to claim 48, wherein the method includes repeating steps a) toe) until the entire length of the tubular (12) is expanded.
 50. A methodof radially expanding a tubular comprising the steps of applyingpressurised fluid to one or more driver devices (20, 22) that arecoupled to an expander device (14), where fluid collects in a fluidchamber (28, 30) and acts on the or each driver device (20, 22) to movethe expander device (14).
 51. A method according to claim 50, whereinthe method includes the additional step of gripping the tubular (12)during expansion.
 52. A method according to claim 51, wherein the stepof gripping the tubular (12) comprises actuating one or more anchoringdevices (36, 40) to grip the tubular (12).
 53. A method according toclaim 52, the method including one, some or all of the additional stepsof a) reducing the fluid pressure applied to the or each driver device(20, 22); b) releasing the or each anchoring device (36, 40); c) movingthe expander device (14) to an unexpanded portion of the tubular (12);d) actuating the or each anchoring device (36, 40) to grip the tubular(12); and e) increasing the fluid pressure applied to the or each driverdevice (20, 22) to move the expander device (14) to expand the tubular.54. A method according to claim 53, wherein the method includesrepeating steps a) to e) until the entire length of the tubular (12) isexpanded.